Method of producing electroplated containers



Oct. 6, 1959 1 L. PEAR-r ETAL METHOD OF PRODUCING ELECTROPLATED CONTAIERS Filed Feb. 29,1956

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United States Patent() Mice METHOD OF PRODUCING ELECTROPLATED CONTAINERS Leland L. Peart, El Cerrito, and Joseph Edward Kettman, Newark, Calif., assignors to Rheem Manufacturing Company, Richmond, Calif., a corporation of CaliforniavApplication February 29, 1956, Serin N6. 568,632

3 claims. (c1. zo4z6) `The plating `process is a well developed art, and from the more `basic `hot dip method, electroplating has come `into widespread commercial use. While hotdipping Vgivesexcellent results, it has the primary disadvantage of using excessive quantities of tin or other plating material. 1 Electroplating is somewhat more complicated, but it possesses the advantage of controlling the thickness of kthe plating to any desired'amount. Accordingly, for most large production jobs, economy dictates the use of electroplating, rather than the hot dip method ,where the plating material is relatively costly, such as in the case of tin, nickel, and the like.

, No `particular problems are encountered` where a smooth surface Vis involved, 1but where a welded seam is present, it fhas heretofore been found difficult, if not impossible, to electro'plate over the weld areaand provide aplating" equivalent tothat' produced remote from the weld area. This inferiorplating results `from the `fact'that,following thewelding, the base metal surface is pitted,` i.e., has recesses, vpockets-and cracks, some being clearly visible to the naked eye, and others being of microscopic character. In any event, during the plating operation, the current tends toitake thepaths of least resistance?, and consequently the plating will flow to the from the "difliculty in cleaning the smaller cracks, `and vthe fill-ing of the pockets with gas formed during the electroplating, which further interferes with `the plating owing therein.- iIhus, examination of electroplated containers manufactured with conventional methods revealed excessive plating porosity in the'zone of the side seam weld.

` -lt is therefore an object of the present invention to provideamethod "of electroplating .a metal 'surface hav- L ing a weld area thereinin which the plating or coating material may be kept at a minimum thickness while still insuring substantial freedom from" porosity in the weld area.-" u u VAnother object of this invention `is tofprovide a method` of electroplating the interior surface of` a metal container having a welded side se'am in which the weld is further objectioftheginvention is to `provide a .methodV ofthe rcharacter described in which an improved oil bath is provided for the-fusing operation, `suchjbath incorporating a desired ztluxing action which removes any high areaslsurrounding suchpockets or cracks rather Athan ll the same. l' Theforegoing situation further results 2,907,701 Patented Oct. 6, 1959 microscopic oxide lm and serves to protect the surface against further oxidation, as well as having a sufciently high ash point to eliminate re hazards, and which possesses other features of advantage.

A still further object of this invention is to provide a method of electroplating a metal container in which the container shell side seam is flash welded, the excessive weld metal is breached, the weld seam is compacted, and the welded shell is then subjected to a generally conventional electroplating operation.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred method of the invention which is diagrammatically illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made `by the said description may be adopted within the scope of the invention as set forth in the claims. l Y

Referring to said drawing: The` gure is a diagrammatic representation of the major steps performed during the carrying out of the method ofthe present invention. H

As hereinabove discussed, the method presentlyrtoy be described is particularly well adapted for the electroplating of metal containers having a welded side seam, and the process will be primarily` described in connection with tin plating wherein a coating of tinapproximately .0002 inch in thickness is electrodepositedy over the 'entire inner surface of the container, including the weld area. However, it will be later discussed how this same process` may be utilized` with other plating materials.

As will be understood, in the manufacture of metal containers, the steel or other base metal from which thefbodyor shell is fabricated is rolled into generally cylindrical form and `then provided with a longitudinally extending Weld, usually referred to as a side seam.` Conventionally, the weld is of the 'lap joint type, but as will be later explained, While this type of joint is possible, it possesses' certain disadvantages from a plating standpoint. Accordingly, in the manufacture of the container 6, as will be seen -in the drawing, the ends 7 are irs't placed in butting relationship, and such ends areash welded together. As is well known, llash` welding is accomplished by passing sufficient electric current through the butting pieces to melt and fuse them together, while at `the `same .time applying pressure in the direction of the arrows to insure a strong joint of compressed fused material. p i i y `Following the flash welding operation, due tothe resulting boiling4 out of the metal, the welded seam 81 will include `a protrusion 9 of metal extending generally radially inwardly and outwardly of the shell surfaces. The next step is the removal of Ithese protrusions, and this is preferably effected `by a stripping or breaching operation. This may be accomplished by using `a series of cutter blades, eac-h successive blade removing a thin layer of the protuding metal 9 until'the side seam has a crosssectional form such as .that illustrated in the sketch entitled stripped seam. .The stripping operation mustpbe carefully performed as it is` necessary'to nishup with` a seam'of substantially uniform thickness without tears or the like appearing therein.` Y l l `After the seam has been properly stripped, the `seam is rolled with a pair of pressure rolls` 12er the like. The width of the rolls is substantially greaterfthan `the width of the `stripped seam, `and the peripheral surfacesof` the respective rolls areof complementaryform, ithatis, kthe inner rollhas a convex surface and the `outer` roll has a, concave surface, each surface havingfa curvaturesubstantially equal to that of the-container itself.-` The aetion of these pressure rolls 12 on the cold seam area is" to smooth out any small ridges resulting from the stripping operation, and more important, to compact the metal in the seam area. By compacting the metal, any microscopic pores or tears will be closed, and there will be insured a'density of steel at least equivalent to the'cold rolled surface on the'remaining portions of the drum '6.

The foregoing description deals with' the preferred manner of side seaming to place the container body in Optimumk condition for electroplating, since the recesses, pockets, cracks, etc. resulting Vfrom conventional welding practices and which would materially interfere with proper plating, have been substantially eliminated. However, it should be made clear that while the ash welding procedure may be preferable, tests have indicated that acceptable plating may be obtained where the welded seam is of'the lap joint type. However, here again, it is particularly necessary that the seam be pressure rolled to eliminate-the large recess along the line of overlap of the joint. Here, thel upper or inne-r roll down roll may have the convex surface such as .that previously described while the lower or outer concave roll is provided with a recess into which the compressed metal may ow. Notwithstanding suchan operation even when the rolls 12 follow the welding dies and act while the steel is still hot, it has been ascertained that the surface is pitted, i.e., that cracks, etc. still remain which present the previously-discussed problems during plating.

= Returning now to the further processing of the container shell 6 whose welded side seam has been compacted and/or .smoothed out in one of the foregoing manners, the shell is now ready-for plating, and preferably a generally conventional plating operation is performed. This includes placing the shell in an alkaline electro cleaner to remove surface dirt, oil and other foreign objects and then subjecting the shell to a cold Water rinse. Preferably, a pickling operation is then performed which includes dipping the shell in a sulfuric acid pickling bath `so as to remove any scale from the side seam weld as l dipped in an alkaline electro cleaner to remove any smut picked up during the pickling operation, followed by a cold water rinse.

Where Vtin is the plating material, the shell is then placed directly in the electroplating bath. However, for plating materials such as lead or nickel, the shell -should rst be dipped into a dilute acid bath, such as a 5% hydrochloric acid solution by volume which serves to remove'oxide and neutralize the shell surface. This is followed by a cold water rinse. p

Thus, the shell is now in a conventional plating bath with the tin, lead, nickel or other plating material forming the anode, and the shell comprising the cathode. In accordance with conventional practice, after the electroplating bath, the plated material is merely rinsed and dried. This would be adequate for the inner shell surfaces remote from the weld seam, but at the seam, notwithstanding the compacting operation performed thereon, there remains microscopic `openings into which the plating material will not flow. In many-instances, this would not be a deterrent to use of the container. How- Vever,.vvhere the container is to be used for certain chemicals or foods, it is essential that the porosity of the plating` on the Weld area meet the general standards required Vfor general tin plating or the like.

Accordingly, as an important feature of the-'inven tion, following the electroplating and conventional rinsing, a flow brightening or fusing operation is performed onthe plating, particularly where the plating isy tin. This fusion results in a melting of the plate coating and the molten metal flows along afgenerally level path and will serve to fill any recesses or cracks inthe basemetal which remain even after the weld compacting operation.

Tin plate fusion is not basically new,and heretofore, Vvegetable or animal oils have been utilized as the heat Viscosity at 210 F., SSU 13S-414 Neutralization No .44-1.l8 Iodine No 32-54 Saponication No 5-21 The oil has a flash point of S60-580 F. andv contains 2.5-15.% fatty acid. As tin melts at 450 F., the fusion bath may be maintained atapproximately 500 F. Without danger, and the weak fatty acid content affords the desired iluxing action.

As a specific example, the lfollowing mineral oil was proven satisfactory on tin plate:

By virtue of the acid fluxing actionany microscopic Voxide film isy removed and the surface is protected against further oxidation.

1 As is known, in the electrodepositI of tin, the latteris builtf up as a crystallinestructure. The hot oil removes the crystals, and therefore, following the Ifusion bath, the shell is promptly quenched in a cold solution of trichlorethylene before the crystals can be reformed. This not only cools the metal, but also serves-to remove the major'portion of' oil which'may be adhering to the same. The shell is then vapor degreased by hot tryichlorethylene to furtherclean and lremove any residual oil. The container 6 Vwith its plating` 13 is then completed and ready for such further manufacturing operations as may be required. v Y

With a combination ofjside seamrtreatmentand tin plate fusion, a plated container may be provided which meets the most, exacting porosity requirements.

,What is claimed is: A p v l,

l. The method of constructing-,cylindrical metal shells which comprises welding `opposite edges of a rolled plate 'to provide a cylindrical shell having a longitudinally exaihot mineral oil bathcontaining from 2.5.,to 15% Vof fre'e Vfatty acid maintainedV ata temperatureabove the melting point ofthe metal.

2. The method of ferrous metal fabrication-'Which comprises Awelding opposite edges, of ferrous metalaplate providinga weldedI-seam alon'g'such edges, stripping ex- 4cess weld material. from said` seam and then'ap'plylng 'pressure Vto said stripped weldseainin a :dlrcctlon generally normal tothe plane thereof to compact the weld metal,.electrolytically depositingia layer of .meta-l. upon the surface of the 'ferrous .metaland upon" the'. seam, and then fusing said platedrnetalbyaimmersing'thc ferrous metal-fabrication into a hot mineral oil` .bath

'containing from 2'.5 to f *15%* offreefatt'yl acidv maintained at a temperature above lthefneltingapqint idro.'

3. The method of constructing cylindrical metal shells which comprises welding opposite edges of a rolled plate to provide a cylindrical shell having a longitudinally extending side seam, stripping excess Weld material from said seam and then applying pressure to said strip seam in a direction generally normal to the plane thereof to compact the weld metal and flatten the same, electrolytically depositing a layer of metal upon the inner surface of said shell, and then fusing said metal by immersing the shell into a hot mineral oil bath containing from 2.5 to 15% of -free fatty acid maintained at a temperature above the melting point of the metal.

References Cited in the le of this patent UNITED STATES PATENTS Windsor Oct. 25, Holmes May 2, Young et al. Mar. 10, Fink Nov. 24, Helmore Nov. 2, Stoddard Dec. 12, Neish June 30,

FOREIGN PATENTS Great Britain Apr. 29, Great Britain Dec. 30, 

1. THE METHOD OF CONSTRUCTING CYLINDRICAL METAL SHELLS WHICH COMPRISES WELDING OPPOSITE EDGES OF A ROLLED PLATE TO PROVIDE A CYLINDRICAL SHELL HAVING A LONGITUDINALLY EXTENDING SIDE SEAM, STRIPPING EXCESS WELD MATERIAL FROM SAID SEAM TO LEAVE FLAT RAISED SURFACES OF WELD MATERIAL ALONG SUCH SEAM, APPLYING PRESSURE TO SAID WELD SEAM IN A DIRECTION GENERALLY NORMAL TO THE PLANE THEREOF TO COMPACT THE WELD METAL TO AN EXTEND TO BE SUBSTANTIALLY FLUSH AND CONTINUOUS WITH THE INNER PERIPHERAL SURFACE OF SAID SHELL ADJACENT THE SEAM, ELECTROLYTICALLY DEPOSITING A LAYER OF METAL UPON THE INNER SURFACE OF SAID SHELL, AND THEN FUSING SAID METAL BY IMMERSING THE SHELL INTO A HOT MINERAL OIL BATH CONTAINING FROM 2.5 TO 15% OF FREE FATTY ACID MAINTAINED AT A TEMPERATURE ABOVE THE MELTING POINT OF THE METAL. 